Bijan Siassi

Fetal echocardiography. IV. M-mode assessment of ventricular size and contractility during the second and third trimesters of pregnancy in the normal fetus.

M-mode echocardiographic examination of the right and left ventricles was performed on 82 normal fetuses between 18 and 41 weeks of gestation. The diameter of the right and left ventricles correlated with the biparietal diameter. The right/left ratio of the ventricular diameters remained constant (1:1) throughout gestation. Fractional shortening and mean circumferential shortening of both ventricles were independent of gestational age. The data presented in this paper will allow the clinician to evaluate abnormal fetal conditions that might affect cardiovascular structure and/or function.

Cardiac output in newborn infants with transient myocardial dysfunction

Decreased cardiac output is a common presumption in left ventricular myocardial dysfunction in neonates, but because of a lack of reliable noninvasive techniques, data on cardiac output are missing. We measured cardiac output by pulsed Doppler echocardiography in 22 newborn infants with left ventricular myocardial dysfunction diagnosed by M-mode echocardiography. Eleven neonates had severe perinatal asphyxia, seven had tachypnea, two hypoglycemia, and one septic shock; one had no symptoms. Right ventricular function was abnormal in 13 of the 22 infants. Hypotension was found in eight; cardiac output and stroke volume were low in 20. The abnormalities were more pronounced in infants with asphyxia. Six such infants were given dopamine (4 to 10 micrograms/kg/min). Within 1 hour, arterial blood pressure, cardiac output, stroke volume, and heart rate increased sharply, with normalization of the myocardial contractility; the other echocardiographic abnormalities normalized over 24 to 48 hours. Pulsed Doppler echocardiography is an advance in the detection and evaluation of therapy for left ventricular myocardial dysfunction in the neonate.

Hemodynamic Changes After Low-Dosage Hydrocortisone Administration in Vasopressor-Treated Preterm and Term Neonates

OBJECTIVE. We sought to investigate whether the increase in blood pressure and decrease in vasopressor support after hydrocortisone administration are associated with changes in systemic hemodynamics in neonates who receive high-dosage dopamine to maintain blood pressure at the lowest acceptable levels. METHODS. In this prospective, observational study, preterm and term neonates who required dopamine ≥15 μg/kg per minute to maintain minimum acceptable blood pressure received intravenous hydrocortisone 2 mg/kg followed by up to 4 doses of 1 mg/kg every 12 hours. Fifteen preterm and 5 term neonates without a patent ductus arteriosus composed the study population. Echocardiograms and vascular Doppler studies were performed immediately before the first dose of hydrocortisone and at 1, 2, 6 to 12, 24, and 48 hours thereafter. RESULTS. In the 15 preterm infants, during the first 12 hours of hydrocortisone treatment, the 28% increase in blood pressure paralleled that in the systemic vascular resistance without changes in stroke volume or cardiac output, whereas dopamine dosage decreased. By 24 hours, the dosage of dopamine continued to decrease, whereas stroke volume increased without additional changes in systemic vascular resistance. By 48 hours, dopamine dosage decreased by 72%; blood pressure and stroke volume increased by 31% and 33%, respectively; and systemic vascular resistance and cardiac output tended to be higher (14% and 21%, respectively) compared with baseline. Contractility, global myocardial function, and Doppler indices of blood flow in the middle cerebral and renal artery remained normal and unchanged. The findings in the 5 term infants showed a similar pattern for changes in cardiac function, systemic hemodynamics, and organ blood flow after hydrocortisone administration. CONCLUSIONS. In preterm and term neonates who require high-dosage dopamine to maintain blood pressure at the lowest acceptable levels, hydrocortisone improves blood pressure without compromising cardiac function, systemic perfusion, or cerebral and renal blood flow.

Fetal echocardiography: VII. Doppler color flow mapping: A new technique for the diagnosis of congenital heart disease

One of the difficulties for the fetal sonographer is the complete elucidation of structural defects of the cardiovascular system that are associated with intracardiac or great vessel flow disturbances. With the recent introduction of Doppler color flow mapping, in which blood flow is displayed in color superimposed on a real-time image, it has been impossible to identify flow disturbances in the pediatric and adult patient. This study was undertaken to determine whether Doppler color flow mapping could be used in the fetus to identify normal and abnormal cardiovascular anatomy. Thirty-five normal and high-risk fetuses were examined between 16 and 40 weeks of gestation. Doppler color flow mapping identified normal and abnormal anatomy (ventricular septal defect, atrial septal defect, endocardial fibroelastosis, dysplastic pulmonary valve, and tricuspid regurgitation). It appears that Doppler color flow mapping will add a new dimension to fetal cardiovascular imaging.

Cardiogenic shock associated with perinatal asphyxia in preterm infants

Fetal and neonatal biophysical and biochemical changes were studied in four preterm infants who developed cardiogenic shock as a result of severe perinatal asphyxia. Fetal distress was documented by the presence of severe late and variable decelerations associated with decreased fetal heart rate variability. Severity of fetal acidosis was decumented by scalp and umbilical cord blood pH. Apgar scores at 1, 5, and 10 minutes were all equal to or less than 5. Although the clinical findings shortly after birth resembled respiratory distress syndrome, it was possible to make a primary diagnosis of cardiac failure with the recognition of cardiomegaly, hepatomegaly, electrocardiographic changes of myocardial hypoxia, decreased myocardial contractility, elevated central venous pressure, and severe lactic acidosis. The treatment of heart failure, including use of inotropic agents, resulted in rapid improvement in the clinical condition, with reversal of the abnormal findings within 24 to 36 hours. Concomitant with this improvement, the increase in arterial blood pressure was paralleled by increase in peripheral (toe) temperature.

Effects of metaproterenol on pulmonary mechanics, oxygenation, and ventilation in infants with chronic lung disease

Changes in pulmonary resistance, dynamic compliance, tidal volume, and transcutaneous PO2 and PCO2 after nebulized administration of metaproterenol were evaluated in eight newborn infants (birth weight 650 to 1060 g, gestational age 25 to 28 weeks) with chronic lung disease receiving mechanical ventilation. The infants were monitored continuously before and for 15 minutes after nebulization of metaproterenol during 3 consecutive days at mean age 34 days. There were significant increases in compliance, tidal volume, and tcPO2, and significant decreases in pulmonary resistance and tcPCO2. These data show that bronchospasm contributes significantly to the high pulmonary resistance in preterm infants with chronic lung disease and that metaproterenol is beneficial in the therapy of infants with chronic lung disease requiring mechanical ventilation.

Fetal echocardiography. III. The diagnosis of cardiac arrhythmias using real-time-directed M-mode ultrasound.

A technique that makes use of real-time-directed M-mode echocardiography is described in which the fetal heart is evaluated for suspected cardiac arrhythmias. Simultaneous M-mode recording of aortic, mitral, or tricuspid valvular leaflet excursion and/or atrioventricular wall motion defines timing relationships between atrial and ventricular systole. With the use of the techniques described in this report, normal as well as abnormal atrioventricular contractions can be quantitated and cardiac arrhythmias accurately defined.

Pulsed Doppler Measurement of Left Ventricular Output as Early Predictor of Symptomatic Patent Ductus arteriosus in Very Preterm Infants

High left ventricular output (LVO) values are associated with symptomatic left-to-right ductal shunting in preterm infants. However, LVO data prior to the occurrence of symptomatic patent ductus arteriosus (SPDA) are lacking. To determine whether serial measurements could predict a SPDA, we measured LVO from day 1 until day 10 with pulsed Doppler echocardiography in 25 preterm infants with birth weights of less than 1,250 g and hematocrits of more than 0.40. Eleven infants never developed patent ductus arteriosus symptoms and had LVO values within the normal range (190-310 ml/min/kg) with only minimal daily variations. The remaining 14 infants developed SPDA which required treatment with indomethacin, ductal ligation, or fluid restriction on days 2-5. From day 1 until day 5 their mean LVO values were significantly higher compared to the group without left-to-right ductal shunt and this increase was secondary to higher stroke volume values. An increase in LVO of more than 60 ml/min/kg consistently preceded SPDA by at least 24 h. Serial measurements of LVO using a single-pulsed Doppler approach can be used for early prediction of SPDA.

Mechanics of Breathing after Surgical Ligation of Patent Ductus arteriosus in Newborns with Respiratory Distress Syndrome

The aim of the study was to detect changes in pulmonary function following ligation of a patent ductus arteriosus (PDA). Pulmonary function was recorded in 16 newborns (birth weight 1,081 ± 166 g, gestational age 27.6 ± 1.7 weeks) before and after ligation. No change in resistance of airways or mean airway pressure was observed. We found an increase in dynamic compliance (Cdyn) of 77% (p < 0.01), in tidal volume (TV) of 29% (p = 0.004), and in minute ventilation (MV) of 17% (p < 0.01) after the procedure. We demonstrated that pulmonary function improves after surgical ligation of the PDA. Because of considerable variation in intubated and spontaneously breathing premature newborns, we recommend the analysis of three main parameters: Cdyn, TV and MV for estimation of pulmonary mechanics in these infants.

New endotracheal tube adaptor reducing cardiopulmonary effects of suctioning.

The continuous recordings of arterial oxygen saturation (SaO2) and beat-to-beat heart rate before, during, and after tracheobronchial suctioning were studied in eight preterm infants with severe RDS receiving mechanical ventilation. Two suctioning procedures were alternatively performed in each infant; In procedure A, disconnection of the ventilator and preoxygenation preceded suctioning; in procedure B, a special suction adaptor was used without ventilatory interruption or preoxygenation; 128 suctionings were performed with each procedure and the changes in heart rate (HR) and SaO2 during suctioning were compared. Although in both procedures, HR and SaO2 decreased during suctioning, the degree of bradycardia and arterial blood oxygen desaturation were significantly smaller in magnitude and shorter in duration during procedure B. These data indicate advantages of the suction adaptor in minimizing bradycardia and hypoxia from airway suction.